The present invention relates generally to improvements in implantation of electrically conductive leads in the human body, and more particularly for enhancing the capability to implant leads of extremely small diameter into precise locations within the patient's cardiovascular system or other positions within the body.
As the technology of implantable medical devices has progressed, advances in the technology of electrical leads associated with such devices have produced improvements in lead functionality and maneuverability, and reduction in lead failure rates. The advances in lead technology include a considerable reduction in lead diameter achieved by means of multi-filar wound coils, redundancy, and bipolar leads in which the individual leads are run, not coaxially, but as separate parallel Teflon-insulated wires in a space-wound manner. These leads are referred to as Thin-Line.TM. leads by the manufacturer, Intermedics, Inc. of Angleton, Tex. ("Thin-Line" is a trademark of Intermedics, Inc. for its small diameter leads).
A principal advantage of such thin leads and the composite configurations in which they are run is that the lead--single or composite--can be introduced into and advanced through blood vessels of much smaller lumen diameter than was admissible by leads of the prior art. For example, a Thin-Line bipolar lead may be provided with a size 6 to 7 French body, which can be accommodated by a 2.0 to 2.3 millimeter (mm) lumen, compared to a typical prior art bipolar lead for similar use which has a size 10 to 12 French body that requires a vein of 3.0 to 3.5 mm lumen diameter. Patients' vein sizes differ, and, for various reasons, not all patients are able to accommodate the 10 or 12 French lead sizes that heretofore had to be used in certain blood vessels of the body. As expected, the smaller diameter lead is more likely to be successfully accepted and advanced through the smaller natural venous access following a venous cutdown. Further, in procedures such as puncture and subclavian stick, the size of the puncture aperture and number of potential complications attributable to it are a function of the diameter of the lead to be introduced. A 2.0 mm puncture wound in a subclavian vein, for example, is likely to create considerably fewer problems than a 3.0 mm puncture.
Although improvements abound in procedural aspects and risk reductions from the use of these smaller diameter leads, as the French size of such a lead is decreased, the lead becomes considerably less visible under X-ray fluoroscopy during surgical and medical implant procedures. Consequently, it is more difficult for the physician to maneuver a thin lead associated with a cardiac pacemaker device, for example, into a desired position in a heart chamber, such as at the apex of the right ventricle.
It is a principal aim of the present invention to provide improvements in techniques by which the capability to use such small diameter leads in situations requiring extremely precise placements may be considerable enhanced.